This application is based on and claims priority to Japanese Patent Applications No. 11-162559, filed Jun. 9, 1999, No. 11-165708, filed Jun. 11, 1999 and No. 11-173957, filed Jun. 21, 1999, the entire contents of which are hereby expressly incorporated by reference.
1. Field of the Invention
This invention relates to a fuel injection system for a marine engine, and more particularly to an improved fuel injection system with corrosion protection.
2. Description of Related Art
In all fields of engine design, there is an increasing emphasis on obtaining more effective emission control, better fuel economy and, at the same time, continuing to increase power output. This trend has resulted in the substitution of fuel injection systems for carburetors as the engine charge former.
Fuel injection systems typically inject fuel into the air intake manifold. In addition, direct injection systems are being considered to obtain still better engine performance. The direct fuel injection systems inject fuel directly into the combustion chamber and potentially have significant advantages over the indirect fuel injection systems including improved emission control.
Marine engines such as for outboard motors can employ direct or indirect fuel injection systems. Fuel for such systems typically is stored fuel tanks that are usually placed in the hulls of associated watercrafts. The watercraft of course is operated in water and hull often contains some amount of water at the location of the fuel tank. The user or operator thus fills the tank with fuel under the conditions that present the possibility of water entering the tank and mixing with the fuel.
Water within the fuel injection system tends to damage the system, especially if salt water is introduced into the system. Fuel injection systems are typically provided with fuel injectors, fuel pumps and regulators, all including elements made of iron that can easily rust in the presence of salt water. The damaging effects of salt water in the fuel supply is particularly detrimental to the fuel injectors. Fuel injectors are extremely precise and delicate, and do not function properly once rusted.
An aspect of the present invention involves the recognition that the introduction of a lubricant into the fuel reduces corrosion of the internal components within the fuel system, especially the internal components of the fuel injectors. If the fuel injected into the combustion chambers contains too much lubricant, however, lubricant is not only wasted, but it also produces white smoke in the exhaust gases and fouls the spark plugs of the engine, i.e., the spark plugs fail to spark due to deposits, which the lubricant likely produces, on their electrodes.
The present fuel injection system thus inhibits corrosion of its components, in the event that water, particularly salt water, is inadvertently mixed with fuel, by introducing an amount of lubricant into the fuel delivered to the engine through the fuel injection system. The amount of lubricant introduced into the fuel, however, is metered so as not to waste lubricant and to inhibit the presence of white smoke in the engine""s exhaust and the fouling of the engine""s spark plugs.
In one preferred application, a fuel injected, internal combustion engine is provided for a marine propulsion device. The engine comprises a combustion chamber. A fuel delivery system is arranged to deliver fuel for combustion in the combustion chamber. The fuel delivery system includes a fuel injector spraying the fuel. A lubricant delivery system is arranged to deliver lubricant to at least one portion of the engine that needs lubrication. An intermediate lubricant supply system operates between the lubricant delivery system and the fuel delivery system to supply lubricant from the lubricant delivery system to the fuel delivery system where the lubricant is mixed with the fuel. A control device is arranged to control an amount of lubricant supplied to the fuel delivery system through the intermediate lubricant supply system. In a preferred mode, the amount of lubricant delivered to the engine through the lubricant delivery system is greater than the amount of lubricant supplied to the fuel delivery system through the intermediate lubricant supply system.
In accordance with another aspect of the present invention, a method is provided for operating an engine. The engine has a combustion chamber, a fuel delivery system, a lubricant delivery system and a control device. The fuel delivery system includes a fuel injector. The method comprises delivering fuel to the fuel injector through the fuel delivery system and spraying the fuel by the fuel injector into the combustion chamber. Lubricant is delivered to at least one portion of the engine that needs lubrication through the lubricant delivery system. Lubricant also is supplied to the fuel delivery system to mix the lubricant with the fuel. The amount of lubricant supplied is controlled depending upon at least one operating parameter indicative of engine running condition.
Further aspects, features and advantages of this invention will become apparent from the detailed description of the preferred embodiments which follow.